The recovery of unwanted material, such as spilled hydrocarbons on water, sand or other structures, has been an environmental concern for many decades. Oil spilled or leaked from tankers, vessels, docks and offshore wells are just a few of the many examples that continue to threaten our environment. Spills and leaks create havoc with birds and other wildlife that inhabit the water and surrounding areas. As long as the demand for petroleum products exists, spills and leaks will continue to occur, thus requiring prompt attention and clean up.
Oil spills and leaks occur on bodies of water of all types, including those containing fresh, brackish, or salt (sea) water. Recovery of oil may also be required on beaches and coastal lands. In yet other situations, it may be required to recover oil from a source, such as the side of a vessel. The unwanted material may be any hydrocarbon material, including, but not limited to, crude oil, residual fuel oils, and distilled products such as gasoline, kerosene-type jet fuel, diesel fuel, heating oil, etc. The term “oil spill” is used herein to refer to a pool or mass of oil floating on a body of water, and without distinction as to the source of the oil or the manner in which it was released.
Several processes and techniques have been used in the past to facilitate the clean-up of oil spills. Hydrocarbon fuel, oil, and chemical spills occur frequently on a multitude of surfaces. On land, clay sorbents, cellulose or sphagnum products, surfactants, or other bioremedial methods to name a few are used in these situations with the intent of cleaning up the spill in a quick fashion or bioremediating a contaminated soil surface over time. On the water, spills present unique problems and require responders to assess each spill quickly and choose among a variety of spill response products and approaches. Factors such as cold water or broken ice conditions can change the physical state of crude oils making broad application of chemical dispersants more difficult and ineffective.
Various techniques and materials have been used as absorbents in helping to minimize contamination resulting from hydrocarbon fuel, oil, and chemical spills. Absorbents generally function by attracting materials to their pore spaces. Adsorbents such as polypropylene fibers function by hydrophobic nature in water and oleophilic attraction of the oil to wick into the surface area of these example fibers.
Furthermore, various elastomeric materials of the prior art are disclosed regarding A-B-A triblock elastomers for hydrocarbon absorption during environmental cleanup on water. The A-B-A elastomers currently utilized include Styrene-Butadiene-Styrene, SBS or Styrene-Isoprene-Styrene, SIS (U.S. Pat. No. 3,518,183), Styrene-Butadiene-Styrene/Ethylene-Propylene Diene Monomer, SBS/EPDM (U.S. Pat. No. 6,344,519), Styrene-Ethylene-Butylene-Styrene, SEBS (U.S. Pat. Nos. 4,941,978 and 5,104,548), or Styrene-Ethylene-Propylene-Styrene, SEPS (U.S. Pat. No. 6,056,805).
Many of the prior art copolymers used in spill cleanup, due to their absorbent properties, are of the SEBS type copolymer. A SEBS type copolymer is apolystyrene-poly(ethylene/butylene)-polystyrene copolymer. Examples are KRATON G-1650 or KRATON G-1651 or KRATON G-1652 made by Shell Chemical Company. The KRATON G series, produced by anionic polymerization, are block polymers in which the elastomeric portion of the molecule is a saturated olefin polymer of the type ethylene/butylenes. Copolymers of these example types are not biodegradable or environmentally friendly.
Current available products for spill control include clay, kaolin, illite, bentonite, diatomite, hectorite, montmorillonite, attapulgite, silica, silica sand, polypropylene, sodium olyacrylate/polyacrylamides, vermiculite, gypsum, limestone, metal oxides, asphalt, fiberglass, diatomaceous earth, perlite and other materials. Such materials, while satisfactory in function, suffer from certain drawbacks. Many such products contain silica, which poses a hazard to humans. In addition, most such materials are not biodegradable, which is a factor that can limit the options for disposal of the used sorbent material.
Several organic spill control products are described in the art. Examples of such materials include natural fibers such as grass, pre-cooked cereal kernels, sawdust, cellulose, and peat. U.S. Pat. No. 5,492,881 purports to describe a cellulose based sorbent system, where the cellulose has been treated with an additive to render it both hydrophobic and oleophilic so it will selectively remove oil from water. U.S. Pat. No. 4,969,774 purports to describe the use of pre-cooked and puffed cereals for oil removal. Another document, U.S. Pat. No. 5,399,350, purports to disclose a particulate milled seed material in which the lipids have been removed through solvent extraction and wherein the material is designed to remove and disperse oil from open water and solid surfaces. The composition is a solvent-extracted proteinaceous material derived from grain products having oil sorptive properties. Also, U.S. Pat. No. 5,492,881 purports to describe the use of diatomaceous earth, clay, silica, corncob, peatmoss, perlite, polypropylene, sawdust, cellulose, polystyrene, vermiculite, peat and cork to absorb liquids. This composition is taught as a general absorbent; in this document, it is stated that materials that absorb both water and oil are undesirable. U.S. Pat. No. 5,891,937 purports to disclose the use of corn stalks, husks, cobs, and kernels as carriers. U.S. Pat. No. 6,110,323 purports to disclose the use of delignified waste from hulls, straw, stover, and shells as a carrier. Other carriers are purportedly disclosed in U.S. Pat. Nos. 6,383,609 and 6,391,120. Generally, other biodegradable materials such as peat moss, sawdust, hair, feathers, cotton, cork, starch, bagasse, seeds, seed hulls, and other seed components have also been proposed. Materials such as these tend to combine with the oil and render recovery and reclamation more difficult.
In recent years there has been an ever increasing awareness of the devastating environmental damage that can be caused by oil spills. It is well recognized that an extremely important aspect of minimizing damage from an oil spill is the prompt containment and collection of the spilled oil. Effective collection of spilled oil ideally involves the absorption of oil in some absorption medium that can be easily raked or otherwise picked up from the surface upon which the oil has spilled. Nevertheless, despite intensive research and testing, the only absorption substances which are at all suitable for use in cleaning up oil spills involve significant defects or difficulties.
Some conventional oil absorbents currently in commercial use are made from polypropylene. Polypropylene absorbs hydrocarbons but is hydrophobic. That is, it is water repellent. However, polypropylene has a limited oil absorbing capacity, and is not at all biodegradable. Also, polypropylene is quite expensive to use in the large quantities necessary to deal with major oil spills. Other methods for oil removal include using absorbents containing polyethylene films, magnetic materials in combination with polyurethane, such as polyurethane containing iron powder, magnetic separation with magnetite and maghemite, acoustic energy, ultrasonic energy, in-situ combustion of oil, polyether containing isocynate end groups, solidifiers, demulsifying agents, surface washing agents and dispersants combination polymers such as viscose rayon, polyamide fibers and small rubber adhering to the fibers.
Yet other efforts require using fish scale powder or biosurfactants such as rhamnolipid as an environmentally friendly and potentially economically viable remediation option. Efforts also include finding other biodegradable oil absorbent materials suitable for cleaning up oil spills. Other biodegradation agents including micro-organisms capable of degrading hydrocarbons, liposomes, bacterial mixtures, enzymes, or fertilizers have been proposed, however, only some of these are commercially viable. For example, peat moss has been used for this purpose. However, in the form in which it is obtainable commercially, peat moss contains a significant amount of impurities such as a sand and carbon. Also, peat moss does not float on water well and is limited in its absorption capacity for oil. For example, one pound of peat moss will absorb about five pounds of oil. In addition, peat moss is not totally biodegradable. Organoclay made by a reaction of smectite clay and quaternary ammonium compound have also been used as oil spill remediation agents.
Another substance which has been tested for its oil absorbent capacity in cleaning up oil spills is a seaweed-based product that is normally sold as a soil conditioner. This product is sold under the registered trademark, AFRIKELP, and is comprised of a blend of selected brown seaweeds found off the southern coast of the African continent. However, this product is rather expensive and has a limited oil absorption capability. Biodegradable remedies for removing oil from spills also include using coconut coir pit, dried corn cobs in their natural state or raw cotton. Other chemical dispersants, gelling agents, inorganic clays, foam plastics, booms, skimmers are also well known in the art. These existing methods either utilize non-environmentally friendly materials or are not cost-effective. Further, while many of these methods may remove significant quantities of oil, the oil is not easily recovered or reclaimed for use in industry. Therefore useful biodegradable and environmentally friendly cost effective methods for oil recovery and reclamation from oil spills are desired.